U.S. patent number 4,532,151 [Application Number 06/588,869] was granted by the patent office on 1985-07-30 for method for coating a surface with a layer.
This patent grant is currently assigned to HEP Products AB. Invention is credited to Stig Stenlund.
United States Patent |
4,532,151 |
Stenlund |
July 30, 1985 |
Method for coating a surface with a layer
Abstract
In a method for coating a surface with a layer the surface is
first subjected to vacuum in a vacuum zone (V) sealed against the
surface, whereupon liquid for forming the layer is supplied to the
surface in a sealed pressure zone (P) following the vacuum zone.
The supplied liquid is then spread out in a controlled manner,
preferably by the sealing (13) terminating the pressure zone. FIG.
1.
Inventors: |
Stenlund; Stig (Saltsjobaden,
SE) |
Assignee: |
HEP Products AB (Alvsjo,
SE)
|
Family
ID: |
20347099 |
Appl.
No.: |
06/588,869 |
Filed: |
February 15, 1984 |
PCT
Filed: |
June 17, 1983 |
PCT No.: |
PCT/SE83/00250 |
371
Date: |
February 15, 1984 |
102(e)
Date: |
February 15, 1984 |
PCT
Pub. No.: |
WO84/00016 |
PCT
Pub. Date: |
January 05, 1984 |
Foreign Application Priority Data
|
|
|
|
|
Jun 18, 1982 [SE] |
|
|
8203782 |
|
Current U.S.
Class: |
427/508; 118/408;
118/50.1; 118/642; 427/238; 427/294; 427/295 |
Current CPC
Class: |
B05D
1/265 (20130101); B05D 7/222 (20130101); B05D
3/0493 (20130101) |
Current International
Class: |
B05D
7/22 (20060101); B05D 1/42 (20060101); B05D
1/26 (20060101); B05D 1/40 (20060101); B05D
003/06 (); B05D 007/22 (); C23C 013/08 (); B05C
003/02 () |
Field of
Search: |
;118/50,407,408,50.1,642
;427/294,295,238,54.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lusignan; Michael R.
Attorney, Agent or Firm: Pollock, Vande Sande and Priddy
Claims
I claim:
1. A method of coating a surface comprising the steps of
establishing a first zone which is disposed in sealed relation to a
portion of said surface and which is movable relative to said
surface in a defined direction, establishing at least one further
zone which is disposed in sealed relation to a further portion of
said surface and which is movable relative to said surface in said
defined direction together with said first zone, said further zone
being located behind said first zone in said defined direction of
movement, evacuating said first zone to clean the portion of said
surface adjacent said first zone and to remove air and impurities
from pores in the said portion of said surface, supplying under
pressure to said further zone a liquid to be coated onto said
surface, said evacuating and liquid supplying steps being effected
while said first and further zones are being moved relative to said
surface in said defined direction thereby to cause said liquid in
said further zone to be coated onto a portion of said surface which
had previously been cleaned in said first zone as said zones are
moved relative to said surface, and spreading said liquid to a
desired layer thickness during said relative movement between said
zones and said surface.
2. The method of claim 1 wherein said spreading step is effected by
a sealing member which is used to seal the trailing edge of said
further zone to said surface and which is movable together with
said zones relative to said surface.
3. The method of claim 1 or 2 including the step of machining said
surface plastically adjacent the leading edge of said further zone
while said zones are being moved relative to said surface thereby
to improve the profile of the portion of said surface which is
thereafter coated with said liquid in said further zone.
4. The method of claim 1 wherein said further zone comprises at
least two pressure zone sections which are disposed one after the
other in said defined direction of movement.
5. The method of claim 4 wherein different liquids are applied
under pressure to different ones of said pressure zone sections
respectively.
6. The method of claim 1 wherein said surface has a cylindrical
configuration.
7. The method of claim 1 wherein said liquid is slide lacquer.
8. The method of claim 1 wherein said liquid comprises a material
which hardens when irradiated with ultraviolet rays, said method
including the step of so irradiating the liquid which has been
spread to a desired layer thickness during said relative movement
between said zones and said surface.
9. An apparatus for coating a surface with a layer of liquid
comprising a device disposed adjacent said surface for movement
relative to and in sliding engagement with said surface, said
device including first seal means in sliding engagement with said
surface for defining a vacuum zone which is sealed against and
movable relative to said surface, said vacuum zone being connected
to a vacuum pump and being operative to remove air and impurities
from the portion of the surface and from pores in said portion of
the surface adjacent to said vacuum zone; said device including
further seal means in sliding engagement with said surface for
defining a pressure zone which follows said vacuum zone and which
is sealed against said surface for movement relative to said
surface together with said vacuum zone, said pressure zone being
connected to a liquid source for supplying liquid under pressure to
a portion of said surface previously treated in said vacuum zone
during movement of said device relative to said surface; said
device further including means for spreading the liquid supplied to
said pressure zone onto said surface portion in a controlled manner
and to desired thickness; and means for effecting relative movement
between said surface and said device.
10. The apparatus of claim 9 wherein said vacuum and pressure zones
are spaced from one another by a common sealing member.
11. The apparatus of claim 9 or 10 wherein said spreading means
consists of a sealing member located at the trailing edge of said
pressure zone.
12. The apparatus of claim 9 wherein said device includes means for
plastic machining the surface prior to said spreading of the
liquid.
Description
The present invention relates to a method for coating a surface
with a layer by supplying liquid under pressure. The invention for
instance relates to a coating of a layer on cylindrical surfaces
and piston rods in pneumatic and hydraulic systems in order to
increase their life and sealing effect.
BACKGROUND OF THE INVENTION
In for instance pneumatic systems, which to a great extent are used
for mechanizing and automating heavy as well as light working
conditions, oil mist is added to the compressed air via a so called
oil mist lubrication aggregate for the pneumatic system to
function. Since, however, this has a detrimental effect on the
working environment and is dangerous to the health, it has for many
years been an aim to cease using the admixture of oil mist.
With oil-free compressed air great demands must of necessity be put
upon the pneumatic components. These great demands have
comparatively well been met as to valve components. However, for
instance concerning cylinders and pistons the problems to achieve
required life and sealing against cylinder pipe and piston rod have
not been overcome. The cylinder pipe is today among other things
for corrosion reasons practically always made of aluminum--like
many other pneumatic components, and the demands upon the inner
surface of the aluminum pipe are satisfactory resistance to wear
and low friction even when there is lack of lubricant. Moreover, a
surface coating must be well adhering. In attempts to meet these
demands there are method based on anodic treatment and Teflon
(trademark) inpregnation. A disadvantage with these methods is that
they are difficult to carry out in long pipes and this fact in
combination with the comparatively large surfaces existing in
pneumatic cylinders means, that the product becomes comparatively
very expensive. As to piston rods, which usually are hard chromium
plated, they must have a very fine surface but nevertheless great
surface wear is obtained. Moreover, chromium is porous and often
has crack formations and therefore action of rust and damages are
obtained resulting in lowered life. In the dry state, i.e. without
lubrication, the anodically treated surface and the chromium coated
surface files off the sealings, usually sealings of rubber, and
oxides of aluminum and chromium particles in-baked in sealing,
piston guide and bushing wear on the pipe and the piston rod and
deteriorate the surface. An accelerated wear course is obtained
resulting in unsatisfactory life and sealing. Due to this one has
been restricted to use a continuous lubrication with oil mist, in
spite of the above mentioned disadvantages, often in combination
with an initial lubrication with grease.
In hydraulic systems, in which the above mentioned problems with
lubrication do not exist, one has, however, an essentially higher
pressure and stress on the sealing surfaces. For obtaining a
sealing satisfactory from the wear point of view the formation and
maintenance of an oil film between sealing and co-operating
surfaces is, however, required as well as a surface having high
surface fineness. However, for practical and economic reasons the
surfaces are too rough for obtaining quite a satisfactory result in
this connection. The result of this is among other things that also
with finest conceivable surfaces the sealings must be exchanged
owing to wear down. When using for instance chromium-plated piston
rods there are furthermore the above mentioned problems in view of
the fact that chromium is porous and often has crack
formations.
SUMMARY OF THE INVENTION
By the present invention the above mentioned problems and
disadvantages have been eliminated and at the same time several
advantages have been achieved. This is not only valid for said
connection in pneumatic and hydraulic systems and with aluminum or
chromium as the basic material, but the invention is highly useful
for coating a surface of another material, both homogeneous and
porous, as well as interior and exterior surfaces having round or
plane shape. Summing up, the following advantages are achieved by
the present invention:
The coating method is cheap and rapid.
The coating material, i.e. the liquid supplied under pressure, can
be cheap.
Large surfaces can be coated at a low cost, for instance pipes and
rods in long lengths.
The adhesion to underlying material is very good.
Besides the good adhesion a very good protection against corrosion
is made possible.
The thickness of the coating can be controlled within close
limits.
The coating method does not require great investments and long flow
times, for instance as is the case in furnace hardening.
The coating method is not combined with risks for the working
environment, as for instance upon lubrication with oil mist.
The attainment of above mentioned advantages has been made possible
by the characterizing method steps according to the invention to
subject the surface to be coated for vacuum in a vacuum zone sealed
against the surface, to supply the liquid to said surface, which
has been subjected to vacuum, in a pressure zone sealed against the
surface, and spreading the liquid in a controlled manner to desired
liquid thickness, wherein said steps are carried out during
relative movement between the surface and said zones.
The invention makes possible the use of liquid according to the
coating desired on the surface. The liquid can be chosen such that
the coating becomes lubricating, i.e. a more or less flowing or
semisolid coating, or liquid that hardens, for instance right up to
enamel hardness, can be chosen. When, for instance, coating
pneumatic parts, as for instance the above mentioned pipes of
aluminum, in order to coat the surface with a good adhesive and
penetrating layer having high wearing resistance and low friction
even when lubricant is lacking this can be carried out in a simple
and reliable manner with the method according to the invention.
Preferably, slide lacquer or corresponding surface-improving liquid
is used. A coating of surfaces on components in hydraulic systems
creates a surface improved in wearing point of view with obtained
and maintained film between sealing and surface which is perfectly
satisfactory.
By the fact that the surface to be coated is subjected to vacuum
before the spreading (painting) of the liquid, a very good adhesion
of the coating is obtained. Owing to this, the liquid supplied in
the pressure zone penetrates down into the pores in the surface and
besides the good adhesion an improved corrosion protection is
hereby obtained, for instance when lacquer is coated on anodized
aluminum surfaces (for instance cylinder pipes) or chromate steel
rods (for instance piston rods). Moreover, the spreading can
according to the invention easily be controlled in respect to layer
thickness for a certain liquid and its viscosity by choice of
pressure, of relative velocity between the used coating device and
the surface and of the shape of the sealing. Thus, the invention
makes possible an accurate control of the layer thickness owing to
the characteristics of the hydrodynamic film formation at the
sealing.
In a preferred method according to the invention the spreading of
the liquid is carried out by the sealing terminating the pressure
zone. This provides for a particularly simple coating device. A
sealing in the form of an O-ring can advantageously be used as a
sealing operating as a very fine and exact "brush".
In cases an improved surface profile is desired, this can in
accordance with the invention in an advantageous manner be carried
out by plastic machining of the surface in the pressure zone prior
to the spreading of the liquid, for instance by drawing.
Under certain circumstances it can be advantageous to coat a
surface with more than one layer. This can according to the
invention easily be carried out by supplying the liquid to at least
two pressure zones positioned after each other and carry out the
spreading by a sealing terminating each pressure zone. The
possibility of supplying different liquids to the pressure zones is
hereby also made possible.
Further characteristics and advantages of the invention will be
evident from the following description of embodiments of the
invention with reference to the accompanying drawings and to the
claims following the description.
DRAWINGS
FIG. 1 is a central longitudinal section through an apparatus for
internal coating of pipes.
FIG. 2 is a longitudinal section through a sealing carrier in
another form than that shown in FIG. 1.
FIG. 3 shows in larger scale a part of the sealing carrier
according to FIG. 2.
FIG. 4 is a section along the line IV--IV in FIG. 2.
DESCRIPTION OF PREFERRED EMBODIMENTS
The shown apparatus is constructed for coating the internal surface
of pipe or tube 10 with appropriate liquid, for instance slide
lacquer. By means of a sealing carrier 11 provided with sealings 12
and 13 a vacuum zone V and a pressure zone P, respectively, have
been created against the tube 10. Sliding sleeve sealings 14 can,
as shown, be arranged outside of the sealings 12. Moreover, a
selected number of sealings 15 abutting the pipe are arranged in
the sealing carrier ahead of the vacuum zone in the draw direction
D of the apparatus.
For the supply of liquid to the pressure zone P the apparatus has a
central channel 16 connected to a cylinder space 17, in which a
piston 18 is running. The piston is driven by a gas accumulator 19
arranged therein which via channel 20 in end piece 21 is connected
to a connection 22 for the supply of gas to the accumulator. The
liquid is supplied to the channel 16 and the cylinder space 17
prior to the insertion of the apparatus in the tube 10 via a
connection 23 to the channel 16 and upon the operation of the
piston 18 the liquid is pressed via a channel 24 in communication
with the channel 16 past a valve 25 in its open position to a
central space 26 and from this space via channels 27 in the sealing
carrier 11 to the pressure zone P.
Vacuum in the vacuum zone V is obtained via a connection 28 to a
vacuum hose from a vacuum pump, via channels 29-34 in the
apparatus, via valve 35 and via channels 36 in the sealing
carrier.
In an apparatus as shown for coating the interior surface in pipes
the vacuum valve 35 is preferably constructed such that the valve
automatically opens, when the apparatus is inserted into the pipe,
and automatically closes when the apparatus is removed from the
pipe.
The liquid valve 25 is in FIG. 1 shown in two positions, namely
above the central line of the figure in completely open position
and below the central line in closed position. The valve is opened
by displacement of its needle 37 from the valve seat 38 against the
action of a tension spring 39 and the displacement is carried out
by a rod 40, which like the needle 37 is shown in two positions
above and below the central line of the figure, respectively.
The apparatus shown in FIG. 1 operates in the following manner.
When the apparatus with a velocity adapted to the liquid flow to
the pressure zone P is drawn through the pipe, for instance by
means of a draw rod 41 screwed into the end piece 21, the interior
surface of the pipe is first subjected to vacuum in the sealed
vacuum zone V, whereupon in the succeeding pressure zone P the
liquid is supplied to the surface and also is pressed down into
possible pores in the surface. The liquid is then spread out in a
very even and thin layer and in the illustrated apparatus this
spreading is carried out by means of the sealing 13 terminating the
pressure zone, which accordingly also functions as a "brush". The
thickness of the layer can be controlled by choice of sealing type,
the viscosity of the liquid, pressure and draw velocity. The choice
of these data can be done by means of a non-dimension figure, which
is the same figure as is used upon analysis of hydrodynamic slide
bearings (for instance in internal combustion engines) and upon
analysis of sealings for hydraulic cylinders.
The sealings 15 positioned in the draw direction ahead of the
vacuum zone V can be a practical complement to the coating device
by improving the surface ahead of the vacuum zone and breaking down
possibly existing extreme tops in the surface profile.
Another embodiment of a sealing carrier 42 corresponding to the
sealing carrier 11 in FIG. 1 is shown in FIGS. 2 and 3. This
sealing carrier 42 is provided with a drawing punch 43 having a
drawing surface 44, by means of which the pipe surface is before
the spreading of the liquid plastically machined in order to
improve the surface profile. In this embodiment the liquid is via
channels 45 and 46 supplied both ahead of and behind the drawing
surface 44. As is best shown in FIG. 3, the drawing surface 44
makes a small angle v with the draw direction of the apparatus.
As the coating liquid, slide lacquer or a corresponding
surface-improving liquid can be used. It can be particularly
advantageous to use a rapid hardening liquid, for instance
polyurethane with photo-initiated cross binding which rapidly
hardens upon irradiation with ultraviolet rays. Such a UV-lamp 47
is schematically shown in FIG. 1 arranged at a socket 48.
The invention is not limited to the embodiment described above and
shown on the drawings but can be varied in several ways within the
scope of the following claims for carrying out a method for surface
coating according to the invention. The method according to the
invention can with adapted constructive configuration of the
apparatus be carried out externally on pipes and rods as well as on
other round surfaces than cylindrical as well as also on plane
surfaces. The essence of the invention is that the used apparatus
has against the surface in question a sealed vacuum zone followed
by a sealed pressure zone having means for spreading the liquid to
be coated and these method steps shall be carried out during
relative movement between the apparatus and the surface. Moreover,
if several layers shall be coated on the surface and/or different
kind of liquids shall be used, more than one pressure zone can be
arranged in the apparatus with supply of liquid to each pressure
zone. For the plastic machining of the surface in the pressure zone
another means than drawing punch can be arranged as well as several
such means or drawing punches in the pressure zone or in pressure
zones positioned after each other. It can finally be mentioned,
that instead of having the apparatus movable relative to the
surface, as shown on the drawings, the surface can be movable
relative to a stationary apparatus or both the apparatus and the
surface can be movable during the coating.
* * * * *